This invention relates to methods for forming insulating thin films for semiconductor devices wherein the method can induce condensation of silanol and dehydration to a high degree at or near ambient pressure. This invention also relates to a semiconductor device comprising an insulating thin film produced by the method of this invention wherein conductive layer corrosion is inhibited, deterioration in insulating film performance is inhibited, and an increase in contact resistance between the upper and lower level interconnects in multilevel interconnect structures is inhibited.
The increasing miniaturization of semiconductor elements (i.e., the increasingly high level of integration of semiconductor devices) has led to the use of multilevel interconnect structures on semiconductor substrates. Silicon oxide films produced by such methods as CVD and spin coating are generally used for the insulating films in semiconductor devices that contain such multilevel interconnect structures.
Semiconductor devices that contain multilevel interconnect structures can be fabricated by forming the lower level interconnects on the semiconductor substrate with separation therefrom by an interposed insulating layer; thereafter forming an interlevel dielectric layer; elaborating via holes to the lower level interconnects by selectively etching this interlevel dielectric layer; and filling these via holes with metal to create an electrical connection between the lower level interconnects and the upper level interconnects.
However, when the silicon oxide film interlevel dielectric layers are exposed to, for example, the reagent solutions used for resist film removal during the etching step, large numbers of hydrophilic silanol groups (Sixe2x80x94OH) are produced in the thin film. This causes the problem of an increased hygroscopicity or moisture absorptivity by the film. The resulting absorption of moisture by the interlevel dielectric level can end up causing corrosion of the conductive layer and a deterioration in the insulating performance of the interlevel dielectric layer. In addition, moisture that has become bound on the surface of the interlevel dielectric layer and/or has entered its interior can produce defects by outmigrating from the interlevel dielectric layer during the process of filling the via holes with metal and thereby increasing the contact resistance between the lower level interconnects and upper level interconnects. This activity becomes very significant as via holes shrink in size accompanying the miniaturization of semiconductor elements.
One countermeasure to this problem is to induce a very thorough condensation of the silanol and dehydration by heating the semiconductor substratexe2x80x94after via hole formation in the interlevel dielectric layerxe2x80x94under a high vacuum around 10xe2x88x928 torr. This approach, however, requires the use of a vacuum plant capable of creating a high vacuum around 10xe2x88x928 torr and as a result is associated with such negatives as raising the cost of semiconductor device fabrication and making process control more difficult.
An object of the this invention is to provide a method for forming insulating thin films that can induce a high degree of condensation of the silanol groups and dehydration at or near ambient pressure, that is, at ambient pressure, or a slightly increased pressure, or a slightly reduced pressure.
Another object of this invention is to provide a semiconductor device and method for fabricating in which conductive layer corrosion is inhibited, deterioration in insulating thin film performance is inhibited, and an increase in contact resistance between upper and lower level interconnects in multilevel interconnect structures is inhibited.
This invention pertains to a method for forming insulating thin films wherein the method comprises coating hydrogen silsesquioxane resin onto a substrate, curing the hydrogen silsesquioxane resin to produce an insulating thin film on the substrate and heat treating the resulting insulating thin film under a pressure of 1 to 1,000 torr at 150 to 550xc2x0 C. A high degree of condensation of silanol and dehydration can be induced in the insulating thin films by the heat treatment.
This invention further pertains to a process for the fabrication of semiconductor devices comprising an interconnect structure comprising at least one electrically conductive layer separated by an interposed insulating thin film wherein the interposed insulating thin film is produced by the method comprising baking hydrogen silsesquioxane resin and heat treating the resulting insulating thin film under a pressure of 1 to 1,000 torr at 150 to 550xc2x0 C.